Modern computer systems often use different processors for different computing tasks. In addition to a central processing unit (CPU), a modern computer may have a graphics processing unit (GPU) dedicated to certain computational tasks in a graphics pipeline, both being potentially part of an accelerated processing unit (APU) that may contain other units as well.
More powerful central processing units (CPUs), graphic processing units (GPUs) and accelerated processing units (APUs) may have higher latency, or latency characteristics that differ from less powerful components. For example, a more powerful GPU may have more stages in its texture pipeline when compared to a less powerful GPU. In such a case, the latency of this pipeline increases. In another example, a more powerful APU may contain a L3 cache for the CPU, compared to a less powerful APU that did not have such a cache. In such a case, the memory latency characteristics differ as the time needed to access data that misses all caches increases for the more powerful APU, but average latency will decrease for the more powerful APU.
The more powerful device and the less powerful device may be able to perform the same processing (e.g., execution of program instructions on the CPU or various programmatic and fixed function operations on the GPU), but differences in latency of this processing may cause the more powerful device to fail to be backwards compatible with respect to the less powerful device. Similarly, there may be differences in speed or throughput of the processing that cause the more powerful device to fail to be backwards compatible. For example, for certain types of processing, the more powerful device may be able to perform more iterations of the processing within the same time interval. Alternatively, the more powerful device could perform the processing using different algorithms that result in behavior that is faster or slower than the less powerful device, depending on the circumstance.
In the case of video game consoles, the operation is typically at a set clock frequency, and the software applications are tested for proper operation at this set frequency. Sometimes, it is desirable to run applications created for the original, less powerful console on a more powerful console. This ability is often referred to as “backward compatibility”. In such cases, it is desirable for the more powerful device to be able to run the application created for the less powerful device without detrimental effects of differences in latency or processing speed.
It is within this context that aspects of the present disclosure arise.